1. Field of the Invention
The present invention relates to a magnetic sensor that employs magnetoresistive elements and that is capable of detecting a vertical magnetic field component.
2. Description of the Related Art
Magnetic sensors employing magnetoresistive elements may be used as, for example, a geomagnetic sensor that detects the earth's magnetic field and is incorporated into a portable device such as a mobile phone.
A geomagnetic sensor is configured to detect each of magnetic field components in the X-axis direction and the Y-axis direction, which are orthogonal to each other in a horizontal plane, and the vertical direction (Z-axis direction) which is orthogonal to the horizontal plane.
For example, in the patent documents Japanese Unexamined Patent Application Publication No. 2003-149312 and No. 2004-61380, a magnetic sensor employing Hall elements is disclosed. In the above patent documents, a configuration of the magnetic sensor is disclosed in which ferrite chips are disposed on the tops of multiple Hall elements and ferrite substrates are disposed on the bottoms of the Hall elements, and in which a magnetic body that extends in the horizontal direction connects the ferrite chips to each other.
It is described that a vertical magnetic field component passes through the Hall elements via the ferrite chips and the ferrite substrates and that a horizontal magnetic field component is oriented in the vertical direction at both ends of the magnetic body and passes through the Hall elements via the ferrite chips and the ferrite substrates (for example, see the paragraphs [0021] and [0022] in Japanese Unexamined Patent Application Publication No. 2003-149312).
In these patent documents, a horizontal magnetic field component may be detected using Hall elements that detect a magnetic field component in the vertical direction with respect to the substrate surface.
However, a magnetic sensor employing Hall elements has a disadvantage that since the magnetic sensor uses ferrite chips, ferrite substrates, and a magnetic body as described in the patent documents, the magnetic sensor has a complicated configuration and uses a large number of parts. Another disadvantage is that the magnetic body which connects the ferrite chips to each other extends a long way in the horizontal direction, so that the size of the magnetic sensor in plan view is larger than that of a typical magnetic sensor and a small-size magnetic sensor may not be achieved. In addition, the Hall elements are required to be disposed separately from each other at both end positions of the magnetic body, causing another disadvantage that a range of choices for installation is narrow, in addition to the above-described disadvantage that a small-size magnetic sensor may not be achieved. Thus, a configuration of a magnetic sensor that detects vertical and horizontal magnetic field components by employing Hall elements fails to improve the production efficiency effectively.
Instead of the magnetic sensor employing Hall elements as described above, a magnetic sensor employing magnetoresistive elements (MR elements) that exert a magnetoresistance effect (MR effect) is capable of detecting a horizontal magnetic field component that is parallel to a substrate surface, but is not capable of detecting a magnetic field component in the vertical direction with respect to the substrate surface. Conceivable ways to make a magnetoresistive element detect a vertical magnetic field component include a way in which the magnetoresistive element is vertically oriented (i.e., the substrate surface on which the magnetoresistive element is formed is oriented in the vertical direction), and a way in which the magnetoresistive element is formed on an inclined surface that is provided on the substrate surface and that is inclined from the horizontal direction toward the height direction.
However, a magnetic sensor employing any of the above-described configurations has a disadvantage that this magnetic sensor may not be manufactured at a low cost, and that non-uniformity of the products is likely to occur and a stable characteristic of magnetic detection fails to be obtained.
The present invention is made to overcome the above-described disadvantages of the related art, and in particular provides a magnetic sensor that employs magnetoresistive elements and that is capable of detecting a vertical magnetic field component easily and properly.